Embodiments of the invention relate to an assembly consisting of a cylinder head and a fuel injector for an internal combustion engine.
Fuel injectors are used in internal combustion engines to supply fuel to the combustion chambers of the internal combustion engine. For this purpose, various construction methods are known for the implementation of the fuel metering. Fuel injectors are used both in gasoline engines, i.e. externally ignited internal combustion engines, and in internal combustion engines with self-ignition, i.e. in diesel engines or dual-fuel engines. The fuel injectors are often arranged in a bore of the cylinder head. It is also possible to provide the fuel injectors in injector sleeves, which in turn are inserted into the cylinder head of the internal combustion engine.
The nozzle opening of a fuel injector is exposed to the high temperatures present in the combustion chamber of the internal combustion engine. The high temperatures at the nozzle opening of the fuel injector on the one hand stress the material of the fuel injector and can lead to its deformation; on the other hand, coking of the fuel can occur, which in turn impairs the function of the fuel injector.
Therefore, there are proposals to cool the fuel injector and, in particular, the tip of the fuel injector facing the combustion chamber.
DE 102 34 324 A1 discloses, for example, a fuel injector in which an outer circumferential surface of the nozzle shaft tapers and the actual nozzle can be designed around it so as to prevent the entry of combustion gases between the nozzle body and the injector sleeve to thereby provide a heat transfer of combustion gases to the nozzle opening (injector tip). A cooling effect of the nozzle opening is thus achieved according to this text by a conical shell element enclosing the nozzle body and sealing it such that no hot combustion gases can penetrate between the nozzle sleeve and the nozzle opening. To improve the heat dissipation, the nozzle shell can be cooled.
The generic DE 3 529 769 A1 shows a heat protection plate for the assembly between the cylinder head of an internal combustion engine and the nozzle holder of an injection nozzle, consisting of an outer annular section axially clamped between the cylinder head and the nozzle holder, and an inner annular flange connected to the annular section, which, with its free inner end, abuts the region of the injection nozzle openings on the nozzle holder in a sealing manner. The heat protection plate (heat shield) serves on the one hand to protect the injection nozzle from heat and, on the other hand, as a seal between the injection nozzle holder and the cylinder head.
A disadvantage of the solutions known from the prior art is that the fuel injector is largely unprotected, in particular in the area of its tip, against a combustion chamber of the internal combustion engine, resulting in a large heat input into the fuel injector.